Conservation and the Gospel of efficiency : the progressive conservation movement, 1890--1920 / by Samuel P. Hays ; with a new pref. by the auth.. - 1st ed.. - New York : Atheneum, [c.1959]. - [14], 297 p. ; 19 cm.см.. - (Atheneum college edition ; 139). - Originally publ. by Harvard Univ. press. - ბიბლიოგრ. შენიშვნ: გვ. 277-282 და ტექსტის შენიშვნ.[MFN: 37796]